Suspension polymerization employing phosphates of submicronic particle size



April 29, 1952 J. M. GRIM SUSPENSION POLYMERIZATION EMPLOYING PHQSPHATESOF SUBMICRONIC PARTICLE SIZE 7 Sheets-Sheet 1 Filed Nov. 18, 1947 INVENTOR. dorm! H.691.

ATTORNEY.

P" 9, 1952 J. M. GRIM SUSPENSION POLYMERIZATION EMPLOYING PHOSPHATES OF'SUBMICRONIC PARTICLE SIZE Filed Nov. 18. 1947 '7 Sheets-Sheet 2INVENTOR. JOHN ('9. GPIM qaam a. M

H 7" TORNE 7 ril- 25,- 1952 J. M. GRIM 2,594,913

7 Sheets-Sheet 3 SUSPENSION POLYMERIZATION EMPLOYING PHOSPHATES OFSUBMICRONIC PARTICLE SIZE Filed NOV. 18, 1947v INVENTOR. JoH/v P2 62:1

ATTORNEY.

Apnl- 29, 1952 J. M. GRlM 2,594,913

SUSPENSION POLYMERIZATION EMPLOYING PHOSPHATES OF SUBMICRONIC PARTICLESIZE Filed- Nov. 18, 1947 7 Sheets-Sheet 4 IN V EN TOR.

JOHN ('7. 6 e102 :4 TTORNE 7.

A nl 29, 1952 J. M. GRIM.

SUSPENSION POLYMERIZATION EMPLOYING PHOSPHATES 0F SUBMICRONIC PARTICLESIZE Filed Nov. 18, 1947 7 Sheets-Sheet. 5

IN V KN TOR. Jaw/v (7. @2102 A fil 29, 1952 7 Sheets-Shet e J. M. GRIMSUSPENSION POLYMERIZATION EMPLOYING PHOSPHATES OF SUBMICRONIC PARTICLESIZE Filed Nov. 18, 1947 INVENTOR. JoH/v ZGzuz ATTORNEY.

J. M. GRIM April 29, 1952 SUSPENSION POLYMERIZATION EMPLOYING PHOSPHATES0F SUBMICRONIC PARTICLE SIZE Filed Nov. 18, 1947 7 Sheets-Sheet 7\CfiHmfiw 20329196 20 @5640 2338 m0 Foul: mm v m u Patented Apr. 29,1952 SUSPENSION POLYMERIZATION EMPLOY- ING PHOSPHATES OF S-UBMICRONICPAR- TICLE SIZE I John Marshall Grim, Pittsburgh, Pa., assignor to-Koppers Company, Inc., Pittsburgh, Pa., a corporation of DelawareApplication November 18, 1947, Serial No. 786,655

completion of the process the polymer settles out as spherical particlesor beads.

It is known that the formation of head polymers of polymerizableethylenic monomers may be accomplished with an aqueous suspension of themonomer in the presence of a dispersing agent which helps to keep theglobules of monomer dispersed during the polymerization. Suchdiiiicultly' soluble phosphates as the calcium, barium, and magnesiumphosphates have been proposed as dispersing agents for this purposebecause of their ability to function as suspension stabilizers foragglomeration inhibitors. Under very restrictive conditions or attendantdisadvantages, as-described hereinafter, these phosphate compounds tendto prevent or diminish the tendency of the globules of the dispersedpolymerizingmonomer or polymerization product to agglomere a'teorcoalesce during the polymerization.

It is now known that these diflicultly soluble phosphates are notcompletely satisfactory for;

this'purpose, and generally thepresent practice of suspensionpolymerization with these dispersing agents is accompanied by a numberof serious limitations. Firstly, an individual phosphate of-this groupmay be unpredictable and erratic in its performance and efficiency inthese polymerizations. In fact, the same chemical entity obtained fromdifferent manufacturers, and sometimes even from the same manufacturer,may be sharply contrasting in its utility for this purpose. "It has beenfound by the present inventor that the difiiculty in obtaining eificientoperation of the diflioultly soluble phosphates as dispersing agents isusually due to the predominance of relatively large particles in suchphosphates.

Secondly, theproductive capacity of suspension polymerization equipmentis restricted to a relatively low output because of the low monomer/ 2water ratio which is required in order to obtain bead polymers ofdesired properties for molding. In producing polymers of sufficientmolecularweight to give the desired properties, it is necessary underpresent practice to use a low monomer/water ratio to prevent thedispersed globules from coalescing completely during the period requiredto obtain the desired polymerization.

On the other hand, and thirdly, if it is desired to increase the ouputof the given equipment by: increasing the monomer/Water ratio, it'isfound that the critical, sticky or gummy phaseof the polymerizationprocess, which is claimed to occur somewhere between 20 and 70%conversion of styrene to polymer, must be made relatively short induration by the use of large amounts of catalyst. These large amounts ofcatalyst apparentlyspeed the polymerization through the sticky phasebefore the globules have the opportunity to coalesce completely, but theresultant high polymerization rates produce polymers havingmolecularweights lower than desired in polymers to be used in the molding trade.

The general purpose and object of the present invention is tocircumvent, simply and effectively, the above-described limitations ofsuspension polymerization processes employing; difficultlysolublephosphates as dispersing agents, or suspension stabilizers, so thatexisting or contem-' plated installations can be optionally employedtoproduce, as required, either high or low cutputsof bead polymers havingeither high or lowmolecular weights. Another object is to provide, forthe stated purpose, suitable phosphates other than those mentionedabove, as well as novel chemical and improved physical forms of thediflicultly soluble phosphates. Still other objects, are to providepolymerization suspensions whichare substantially insensitive toirregularities in' composition or in physical operating conditions,

to provide improved control of bead size and prof vide processes'inwhich reproducible results can be consistently obtained. The inventionhas-for} further objects such other improvements and such otheroperative advantages as may be found to result from the methods andapparatus hereinafter described or claimed.

In the accompanying drawings, Figures 1 2, 3, 4, 5 and 6 are electronmicrographs of phosphate particles of diverse sizes, and Figures 7 and f8 are graphs illustrating certain features of the invention as will bedescribed.

The aforestated objects and others, which will become apparent from thedescription, are accomplished in the present invention by using adiflicultly soluble phosphate containing at least three equivalents ofmetal for each phosphate group and having a particle size which ispredominantly in the order of a submicron, and in some cases furthermodifying the effectiveness of the phosphate with an extender. Theextenders" of this invention comprise anionic surface-active agentswhich aid the diificultly soluble phosphates in giving markedly morestable suspensions which are relatively insensitive to variations in thecomposition of the suspension, and to irregularities in physicaloperating conditions. It has also been found that certain difiicultlysoluble basic phosphates such as hydroxy apatites, are generally moreeffective than other dimcultly soluble phosphates for stabilizing suchsuspensions.

As mentioned above and as illustrated by examples hereinafter, oneobstacle in the way of obtaining desired results consistently withdifficutly soluble phosphates of the prior art was found to be therelatively large size of the phosphate particles. This was indicated bystudies of the particle size of certain difficultly soluble phosphateswhich were quite erratic and unpredictable in their behavior asdispersing agents for suspension polymerization. In investigating theeflect of particle size, the particle sizes of some of these phosphateswhich operated erratically were reduced by milling or grinding to sizespredomin-atly in the order of a sub-miopen. As illustrated later, someof these phosphates which originally operated unsatisfactorily withlarge particle size were improved in etficiency upon reduction of theparticle size.

The term .submicron is used in the sense defined'in' Hackhs ChemicalDictionary, Third Edition, page 813, as meaning a particle between 0.2and 0.005 micron in diameter. The terms extender is applied to theanionic surface-active agents, which act as an adjuvant in boosting orincreasing the capacity or ability of the above-described phosphatedispersing agents to stabilize the suspensions-described herein. Theseextenders give to the phosphate dispersing agents, which have a limitedcapacity or ability to stabilize dispersions, an, additional capacity ofan amount and type over and above that possible by the use of increasedquantities of the phosphates. The results and efiiciency of theiroperation are clearly illustrated in a number of .the examples givenlater.

"Difliculty soluble phosphates are those phosphates which are notclassifiabl as water -soluble phosphates. The term difiicultly soluble"includes in its scope the terms insoluble, very slightly soluble andslightly soluble given in Hackhs Chemical Dictionary, Third Edition,page 787, and is intended to mean that more than 100 parts by weight ofwater are required to dissolve one part by weight of phosphate. In allcases in the practice of this invention, there should be enoughphosphate present to have undissolved phosphate particles in thesuspension system. The-base or metal component of these phosphates maybe any metal whose carbonate is also diflicultly soluble in water. Thus,the metal may be calcium, barium, strontium, magnesium, aluminum, zinc,cadminum, iron and like metals, all of which give difficultly solublephosphates.

Phosphates of the ,iiypeandparticle 'size :de-.

scribed above as suitable for the practice of theinvention may beprepared by precipitation methods. For example, methathetic or doubledecomposition reactions may be used to obtain precipitates ofdifiicultly soluble phosphates, such as the reaction of ortho-phosphoricacid with an appropriate oxide or base, for example, with calcium oxide,or the reaction of a water-soluble salt of ortho-phosphoric acid with anappropriate salt or base, for example, trisodium phosphate with calciumchloride. Phosphate having the desired proportions of three or moreequivalents of metal or base for each phosphate group may be obtained bythe use of stoichiornetric proportions in the double decompositionreactions or by hydrolysis of the secondary or tertiary phosphates.However, a strict adherence to stoichio- .metric proportions of three ormore equivalents of base for each phosphate group is not alwaysnecessary. In some cases, satisfactory products have been obtained withas little as 2.5 equivalents of base for each phosphate group. In somecases, however, it is believed that the products are mixtures ofcompounds containing three or more equivalents of base with compoundscontaining less than three equivalentsof base and that the effectivecomponents of the mixtures are the phosphates contain'ng three or moreequivalents of base. This belief is supported by the fact that, in thesubstantially pure forms, the phosphates of three or more equivalents ofbase have proved efiective in the practice of .the invention, whereas.those phosphates having only two equivalents ,of base, such-as thediflicultly soluble secondaryv calcium ortho phosphate and calcium pyro.phosphate, are ineffective in these processes. I

Depending upon the particular conditions employed in the preparation ofphosphates for the practice ofthe invention, a variety of difierentlyconstituted products may be obtained. These include the normal orthophosphates such as tricalcium phosphate, its hemi -hydrate 2Ca3(PO4)2'I-IzO, which is believed by some to be the salt, CasHzPzOs, ofthe diatomic acid, HaP209. which contains the equivalent of twophosphate groups per molecule, and other hydrates, as well as suchpreferred phosphates as the hydroxy apatites, such as hydroxy, apatite(calcium hydroxy hexaph-osphate) 3Ca3(P O4)2'Ca(OH) 2. which containsthev equivalent of six phosphate groups per molecule, and likephosphates having an apatite lattice; However constiuted, the phosphatesusedinthe practice of the invention are derivatives of ortho-phosphoricacid even though, in a strict sense, they may not'be ortho-phosphates,but may more properly be considered as salts of those phosphoric acidswhich have at least asmuch water of constitution as orthophosphoricacid, and in which salts at least three equivalents of base areassociated in the compounds for each phosphate group.

Where colorless beads are desired, the use of achromatic or colorlessphosphates is preferred. These phosphates are obtained with metalshaving colorless oxides such as aluminum, magnesium, calcium, barium,strontium, zinc and cadmium.

"Surface-active agents are organic compounds which, when present in asolution in sufiicient concentration, have the property of effecting achange in surface phenomena such as the surface tension of the solutionmedium. These agents, as is well known in the art, function by virtuezofanorganophylic group associated with a hydrophylic'group. Anionicsurface-active agents are those surface-active agents in which theorganophylic group is contained in an anion. For example, theorganophylic group may form part of a carboxylate, sulfonate, or sulfateanion. Thus, anionic surface-active agents which have been found usefulas extenders in the practice of this invention include such diversecompounds as sodium caproate, oleic acid andortho-carboxybenzene-azodimethylaniline. It appears, however, that themore active surface-active agents are the more effective extendersaccording to the invention. Soaps, for example, are particularlyeffective. Organic sulfates and sulfonates; such as long chain alkylsulfates and sulfonatesas obtained by'the sulfation or sulfonation ofalcohols and hydrocarbons; alkali sulfite-addition products of neutralesters of unsaturated polycarboxylic acids; alkyl aromatic sulfonatessuch as obtained by the sulfonation of alkylated aromatic hydrocarbons;and aryl'alkylpolyether a dispersing agents in suspensionpolymerization, this tendency of the phosphate particles to agglomerate,if uninhibited, causes the formation of large agglomerates during thepolymerization. For example, afterfive hours of polymerization in thepresence of difiicultly soluble phosphates originally ofsubmicroni-eparticle size, phosphate agglomerates having diameters aslarge as 160 microns were observed. It was found, however, that by theuse of anionic surface-active agents in amounts described later, theagglomerations of the phosphate particles can be controlled.

While no attempt is made to explain the phenomena by which the anionicsurface-active agent, or extender, operates, it is believed that itsability to control flocculation of the phosphate particles is directlyconnected with its utility in extending" the dispersing properties ofthe phosphates in accordance with the invention. Moreover, thesephosphate dispersing agents are extended by specific effective ranges ofconcentrations of "the anionic surface-active agents. In concentrationsbelow or above these ranges, the anionic surface-active agents are notefiective for this purposeand in too high concentrations may have anadverse effect. In fact, concentrations of surface-active agents higherthan these ranges permit the formation of agglomerates even larger thanthe 160 micron agglomerates mentioned above. The use of the termextended phosphate dispersing agent is intended to mean. therefore, aphosphate dispersing agent used in association with the properconcentration of anionic surface active agent for extending or expandingits utility orfunction as a dispersing agent. These limits and ranges ofconcentrations will be discussed ad illustrated hereinafter.

The term extending concentrations, includes those concentrations ofanionic surface active agent which, in the presence of an employedphosphate dispersing agent, do not materially affect the surface tensionof the aqueous phase.

The lower limits on extending concentrations are those concentrationsbelow which the anionic I; rather narrow. These ranges are illustrated'by surface active agent has no apparent effect on i the phosphatedispersing agents according to the plies to surface tension oftheaqueous phase dHf-w: ing the polymerization. For example,with-.highlyzj active surface-active materials there may be a;temporary, initial lowering of the surface tension by about'5-10 dynesper centimeter, as measured" by aDu Nuoy tensiometer.- .fllii'sfinitiallowering is not consequential, however, since the surface tensionresumes its original value after the polymerization has proceeded forsome time. The effect on' the surface tension of adding sodium oleateinan extending concentration is illustrated in Tables I and II. Thisinformation was obtained in connection with polymerizations com ductedat about 90 C., and the surfacetension iwas-measured, at 21f C. F.)witha DufNuoy interfacialtensiometr on the clear liquor which beenallowed to stand forashort mme.

had been siphoned: ofi after the suspensionhad Table I [Suspensioncontaining sodium 'oleate (0.008% based on suse ha pension) and 55%styrene, 0.5% hydroxy apatite,

peroxide (based on styrene), and the balance water.)

Surface Material Tested Tension in Water used in preparing suspension...71 Suspension when originally formed. 63 Suspension after 3 hourspolymcrizat -70 Suspension after 6 hourspolymerization" 74 Suspcnsionafter 10 hours polymerization 74 Table II [Suspension containing sodiumoleete (0.008% based on totaL, suspension) and-160% styrene, 0.5%hydroxy apatite, 0.175%'.

benzoyl peroxide (based on the styrene), and the balance watenl SurfaceMaterial Tested Dynes/c ni Suspension after 5 hours polymerizationSimilar suspension except no styrene, after 5 hours.

Similar suspension except no hydroxy apatite, after 5 hours Water usedin preparing suspension Same water saturated with hydroxy apatite aloneSame water containing 0.02% sodium oleate alone (equivalent toconcentration using 0.008% in suspension) The data inthe above tablesshow that; except;

The amounts of surface-active agents necessary to extend phosphatedispersing agents accords... ing to the invention are not only verysmall but the ranges of concentrations in which they are effective inextending the capacity of the dispersing agents to give stabledispersions-"a the .curves of Figures 7 and 8. Figure 7 illus trates theeffects of three of the-more common surface-active agents. The curvesshoweffectivej g ranges of these surface-active agents or extenders forstabilizing suspensions containing 60 parts; styrene, 40 parts water,0.5% hydroxy apatite (same material and particle size as described laterin Example IV) and 0.175%'benzoy1 peroxide: (based on the styrene) for aPQlYmerization con-f invention. The reference to-surface tension ap- 75ducted at C. The effective itansesjgnthm,

Tension in' 1 do a xenon as three surfaces-active .agentsare given invthe 101-:

lowingstablez- Table I H [Effectivemanges of.surface;actlve. .agentsused with 0.5%

" hyflroxy apatite] Suriace-Actlveuigent Figure 8i11ustrates the effectOn the range of efiective or extending? concentrations of sodium oleatecaused by varying the concentration of the dispersing agent and theconcentration of the. styrene-or dispersed phase. With 0.5% hydroxyapatite and 60% styrene, the range is from 0.0055% to 0.032% based onthe total weight of' the suspension. When the hydroxy apatite isincreased to 2% for 60% styrene, the eifective range of extender for.stability is enlarged to 0.008 to 0.044%. When the styrene content 'isreduced to 40% with 0.5 hydroxy apatite, the effective range of extenderis shifted downward to. 0.001 to 0.028%. While these data establish theexistence of definite concentration ranges in which theanionic'surface-active agents are effective as extenders, it must beunderstood that the limits of these ranges will shift somewhat dependingupon the exact experimental conditions. For

instance, the ranges are affected to some extentby the type and speed ofstirring, the type and shape of the reaction vessel, the type ofmonomer, the type of dispersing agent, etc. However, the range ofextending concentrations of surfaceac'tive agents will'generally bebetween about 0.0005 and about 0.05% based on the total suspension andbetween about 0.1 and about 10% based on the dispersing agent.

The following tableillustrates the wide variety of anionicsurface-active agents which may be used to extend the phosphatedispersing agents,

according tothe invention. Concentrations are given which have beenfound effective under the condit onsdescribed later m Example IV.

Table IV Concentration in percent o1- Surface-active Agent Total DispelSuspensing sion Agent Sodium tetradecyl sulfate (Tergitol 04)". 0, 6Sodium pentadecyl-sulfate ('Iergitol 07) 0.003 0.6 Sodium octyl sulfate(Terg1to108) 0, 005 1, Sodium sulfate of aryl alkyl polyetber suli'onate(Triton 720) 0.008 l. 6 Oleic acid. 0.04 3 Crude sodlumoleote(saponified (1 oil) 0.012 2. 4 Sodium luure 0. 008. 1.6 Sodium caprate0.008 1.6 Sodium caprylate 0.008 1.6 Sodium caproate. 0.024 as Potassiumstearatc 0.008 1. (1 Calcium-oleate'(precipitsted1n situ from sodiumoleate-and C8012) 0.008 1. (i Calcadur-Red BBL-diam dye l. o Azosol-Fast0range-3RA-monoazo dye Mi BriIIiontOm-mine-L 3 0. 003 0.

Sodium salt of 3,31-(1isulfodiphenylurea-4,i'diazo-bis-amino-S-naphtholos'ulfonic acid.

0rtho-curboxybenzene-azo-dimethylanlllne.

Sodium salt of 2;5,2,5f-tetramethyltnpbenylmethane-4,4 diazobisbotanophtlioldisultonic 8686' Concentration in percent The. processes oftheinventionare applicableto suspension polymerizationof anypolymerizable; ethylenic monomer. By the-term polymerizable ethylenicmonomer, it is intended to include any ethylenic compound which ispolymerizable under the conditions of suspension polymerization, that iswith or without catalysts, such asthe peroxide type, for example benzoylperoxide, possibly ethylenic compounds which will not polymerize bythemselves, but will do so in conjunction with other monomers.

More'particularly, the invention is applicableto the polymerization ofvinylaryl monomers, such, as, styrene, orthoor para-monochlorm styrenes,dichlorostyrenes and vinyl naphtha-1' lenes.

By theprocesses of the invention it is possible topolymerize aromaticvinyl monomers to clear beads or pearls in concentrations of aqueoussuspensions and to molecular weights higher than heretofore possiblewith a waterinsoluble phosphate as the dispersing agent.

The application of the processes of the invention to polymerization of avariety of polymerizable ethylenic monomers is illustrated in thefollowing examples. The parts and percentages in the examples andthroughout the specification are by weight unless otherwise specified.In all examplesthe pH of the dispersion media was about 6 at the time ofcompletion of polymerization, except as otherwise indicated. Molecularweight were determined by using toluene as the solvent and by theformula:

(Intrinsic viscosity) =KM where K equals 5.44X 1.0- and 0. equals 0.8.The intrinsic viscosity was determined in the usual manner byextrapolating a viscosity concentration curve to zero.

In order to facilitate study of the examples it maybe well to point outthat they are arranged in such an order as to illustrate various pointsof the invention. Thus Examples I-III, inclusive, show suspensionpolymerizations carried out without phosphate extender. tricalciumphosphate, of the large particle size shown in Figure 3. This exampleshows that concentrations of 30% styreneor higher could not be; usedunder these conditions with l% catalyst. Examples IIand III show thathydroxy apatite of the fine particle sizeshown in Figure l, with 0.4% ormore benzoyl peroxide, permitted higher concentrations of styrene to beused but with the large amounts of catalyst relatively brittle, lowmolecular weight products were obtained.

Examples IV to VI, inclusive, illustrate the effect of sodium oleate asan extender, permitting unusually high concentrations (up to of styreneto be used with only 0.175% benzoyl peroxide (based on the styrene) inthe preparations of beads of polymers having high molecular weights.Example VII shows that even the presence of the extender cannot entirelyor completely compensate for or oifset the disadvantage of largeparticle size in the phosphate dispersing agent. Example VIII furtherillustrates the effect of the extender by showing that thepolymerization may-be conducted, in the absence of catalyst, with 60%styrene to give high molecu lar weight products. In Example IX, theefiects of small catalyst concentrations are shown to-be Example Iuseswere unsuccessful.

*9 reflected in increased molecular weights and improved impactstrengths of the polymer products.

EXAMPLE I an inchin diameter were obtained.

Efiorts to repeat this example with styrene to water ratios of 30 to 70,40 to 60,and 60 to'40 EXAMPLE -II Suspensions preparedfrom 50 parts" ofwater, 0.5 part hydroxy apatite (of a particle size having diameters inthe order of 0.03-0.06 micron as shownin the electron micrograph ofFigure 1) and 50' parts styrene containing difierent amounts of benzoylperoxide were heated at 90 C. with rapid stirring to effectpolymerization. It was found that polymerization could be efiected with0.4% benzoyl peroxide (based upon the styrene), but with 0.3% thesuspensionsiwere not stable.

From these data it will be seen that polymerization may be carried outwith much more concentrated suspensions than in Example. I and with asubstantially lower catalytic activation in suspensions stabilized withphosphate dispersing agents of submicron particle size in accordancewith the invention than with phosphate dispersing agents having a largerparticle size.

.. E AMPLEI I The procedure of Example-II Wasrepeated, using a 60-40styrene'to water ratio. found; that at this concentration the minimumeffective catalyst concentration was 0.6% benzoyl peroxide (based uponthe styrene). At this concentration, however, stable suspensions couldbe maintained only when carried outwith intense agitation. With lessintense agitation, more .than 1% of catalyst was necessary. 1 The datagiven in Examples 1, II, and III show that if the catalyst concentrationis sufficiently high, polymerization can be effected without an extenderat relatively high concentrations of monomer with phosphate dispersingagents of submicronic particle size orat low concentration of monomerwith relatively poor dispersing agents. As it is undesirable in manycases to use such high catalyst concentrations because of the relativelybrittle, low molecular weight polymers obtained, the advantage of usingan extendedfphosphate dispersing agent according to the invention isevident. This is further shown by the data given later in Examples VIIIand IX.

EXAMPLE IV A mixture of 40 parts of distilled water, 0.5 part of hydroxyapatite of a fine particle size described later in this example, 0.008part of sodium oleate, and 60 parts of styrene having dissolved in it0.105 part of benzoyl peroxide (0.175% based on the styrene) wasagitated in a flask provided with an axial impeller type agitator andsuspended swirl bafiles to form a'suspension. The suspension thus formedwas heated at 90 C. with continued agitation in a nitrogen atmospherefor 20 hours. The pH of the dispersion medium, which was 5.6 at thefinish of the polymerization,

- graph.

10 was changed to 2 by the addition of concentrated hydrochloric acid,and the charge centrifuged, washed and dried. Clear :beads havingaverage diameters off; of an inch were obtained.- These beads had amolecular weight of about 228,000 as determined by the above equation.The beads, on

EXAMPLE V The process of Example IV was repeated using '70"partsofstyrene containing dissolved'therein EXAMPLE VI-'Ihe-process-of-Example IV was repeated using 75 parts of styrenecontaining 0.131 part-of benzoyl peroxide (0.175% based on thestyrene)and :fine beads essentially the sameas in Example IV were obtained.

I EXAMPLE VII The procedure of Example IV wasrepeated using a mixture ofparts of distilled water, one part of hydroxy apatite (having a particlesizeof substantially half a micron or more in diameter as, shown inFigure 2, which size is larger than that used in Examples IV, V and VI),0.022 part sodium oleate and 20 parts of styrene having dissolved in it0.035 part benzoyl peroxide (0.175% based on the styrene). Otherwise theconditions were the sameas in Example IV. Beads haying diameters ofbetween about /8 and inch were obtained, e

The relatively large size of the beads obtained as compared with thoseobtained according to Examples IV, V and VI, indicates that thesuspension was less stable. This fact is also shown by the fact that ina duplicate run precipitation occurred before completion of thepolymerization. These results show that hydroxy apatite of particle sizepredominantly-larger than the order of a submicron gives inferiorresults even in the presence of an anionic surface-active agent.

EXAMPLE VIII lyst,"'even with an unusually high ratio of'monomertowater: 'SuSp8IlSi0I1S so formed, unlike those formedwith unextendedphosphate dispersing-agents; are "operative regardless of catalystcontent. This makes it possible to produce bead polymers havinga muchwidervariety of physical properties than heretoforepossiblewithphosphate dispersing agents according to the prior art.

EXAMPLE IX Suspensions, formedwith 40 parts water, 0.5 part. hydroxyapatite asin. Example IV, 60 parts styrene; and. 0.008 part sodiumoleate. and containing; different concentrations .of. benzoyl .peroxide,were polymerized at 90 C. The results are given in the following table;

Table .V

V Viscosity- 4 Izod'Impact Catalyst 1 Concentration Relative ular'(Based onstyrene) (ltZ, So 1u- Intrinsic Weight Bars L lOD'lD. Toluene)ft. lbs. 1. 457 0. 4 74, 000 0. 58 1. 846' 0. 75 161,000 1. 23 2. 4001.00 228.000 1. 67

l ASTM No. D 256431.

Figure 1. This hydroxy' apatite could not be substituted for that usedin Examples IV, V, and VI, and was effective only in much lowerconcentrations of styrene as shown in Example VII. Figure 3 is anelectron micrograph of calcium phosphate hydrate. reagent grade, whichshows 'the' predominance of large dense masses andthe substantial'absence of particles of submicronic size. The material in this form is apoor dispersing agent and cannot be substituted for thehydroxy apatitein Examples IV, V and VI'. However, the dispersing properties ofthismaterial were somewhat improved by rapid stirring and heating inwater for 20 hours so as to reduce the particle size. Dispersingproperties of poor phosphate dispersing agents may sometimes also beimproved by reducing the particle size of the same in a ballmill,colloid mill, or homogenizer. Sometimes; however, the agglomerates arevtoo dense and too hard to be brokentdown easily to small particle sizeby these. treatments. For example, Figure 4 shows an electron micrographof C. P. grade of tricalcium phosphate. magnified 18,500 times, whichhas dense, massive particles that could not be broken by the above meansinto particles of a size suitable for use as dispersing agent.

In the practice of the invention the amount of phosphate dispersingagent-may be varied widely in accordance with the activity of. thedispersing 5- 12 extender or surface-active agent used, etc. Generallyhowever; the amount will be between 0.1% and about 5% or. more otthetotal suspension, although ordinarily not more than about 1% will benecessary.

With a phosphate dispersing agent extended in accordance with theinvention, it is possible also tocontrol' somewhat the size of the beadsproduced merely by adjusting theamount of phosphate dispersing agent andthe" amount of extender or anionicsurface-active agent used in thepolymerization suspension. Usually with the amount of agitation constantthe bead size is quite uniform for-the beads of any. particularrun. butthis uniform size or the average size may be adjusted over awide;range;. For example, beads may be obtained having diameters aslarge as several". millimeters; or beads :may be made, by theadjustments indicated, having "diameters" as small as about'30'microns.However, without an extender forthephosphatedispersing agent, con trolof thebead size isdifllcult and small beads are obtained only withvigorous agitation and with relatively large amounts of catalyst.

Tables VI, VII and VIII show the effect on'the beadsize' caused byvarious concentrations of hydroxyapatite and sodium dodecyl benzenesulfonate orrsodium oleate. In all cases, the polymerizations were runaccording to the procedure in Example IV, with'40 partswater; 60 partsstyrene containing dissolved in it 0.105 parts benzoyl peroxide (0.175%based onthe styrene), and amountsof hydroxy apatite and sodium dodecylbenzene sulfonate' or sodium oleate were used as indicated inthe-tables.-

Table. VI

Average Bead Diu meter in Microns Percent of Hydroxy Apatite Based onTotal Suspension 7 The data given in'this table show that the bead sizedecreases as the-amount of phosphate dispersing agent'is increased to1.75% and then increases-for higher'percentages of dispersing agent Thedata in this table show that the bead size becomes smaller:as the amountof surface-active agent or extender is increased (up to about 0.012%),and then increases for still larger amounts of extender. From the dataof this table, it is obvious that the bead size of the '13polymerization products usually may be controlled over a wide range byselecting suitable proportions of dispersing agent and extender.

Table VIH further illustrates control over bead size by showing theresults obtained by proportionately increasing the concentration of boththe hydroxy apatite and sodium oleate. It will be seen from these datathat the beads become progressively smaller as the amounts of dispersingagent and surface-active agent are increased.

7 Table VIII [Percentages based on total suspension] Average- Percent ofPercent ofHydroxy Apatite Sodium g zg g Oleate Microns While theinvention and the advantages thereof have been illustrated withparticular reference to styrene as the polymerizable ethylenic monomer,particular calcium phosphates as the dispersing agent, and sodium oleateas the extender,

it will be understood that'other like materials the organic sulfonates,sulfates and carboxylates, 7 each organic residue of which contains oneor hydrate consisting of a mixture of tetra and "submicronic.

octa hydrates of normal .trimagnesium phos-i phate. Figure is anelectron micrograph illus tr'ating the particle size of this material tobe Finely divided zinc phosphate was prepared by adding slowly, at roomtemperature and, with stirring, a solution of 424 parts of zinc chloridein 1000 partsjof distilled water to a s0lution,,, ot

718 parts of trisodium phosphate dodecahydrate in 400 parts of water.The pH was adjustedjto neutrality, and an aliquot portionfif thisprepara-} tion was used in the following steps. A A suspension,consisting of 60 parts distilled water, 1 part of the above-preparedzinc phosphate, 0.02 part sodium oleate and 40 parts styrene, havingdissolved in it 0.07 part benzoyl peroxide (0.175% -based on thestyrene) was heated at 90 C. with stirring for hours. The pH of thesuspension medium was 7.2 at the time of completion of thepolymerization. Beads ranging from about to about of an inch in diameterwere obtained.

Finely divided aluminum. phosphate was prepared by adding at roomtemperature and with more alkyl groups totaling up to about 18 carbonatoms, and preferably containing more than 6 carbon atoms.

Also, in place of styrene there may be used 7 various polymerizableethylenic monomers .in-

and IV, showing the use of various extenders, and

in the following examples. Examples X to XIII. inclusive, show theutility of various phosphates as dispersing agents in the practice ofthe invention; and Examples XIV to XXVI, inclusive, illustrate thepreparation of head polymers or copolymers using various polymerizableethylenic monomers or mixtures thereof.

EXAMPLEX A suspension, formed of 40 parts distilled water,

meta

stirring, a solution containing 19.8"parts of alumi num chloridehexahydrate in parts of distilled water to a solution containing 23parts of trisodium phosphate dodecahydrate. in 100 parts of water. ThepH of this solution was 5.5. Analiquot portion of this suspension wasusedjin the following steps. a f

A suspension, consisting Iof. parts distilled water, 1 part of theabove-prepared aluminum phosphate, 0.003 part sodium oleate 'and 40parts styrene containing dissolved in it 0.07, "part benzoyl peroxide(0.175% based on the styrene), was'heated at C. with stirring for 20'hours. The pH of the suspension medium was 5.4 at the time of completionof the polymerization. Beads ranging from about to about 1 3' of aninch-in diameter were obtained. I v

EXAMPLE XIII Finely divided cadmium phosphate prepared by adding, atroom temperature and with stirring, a solution containing 26 partscadmium chloride in partsof distilled water to a solution containing28.8 parts of the sodium phosphate dodecahydrate in 200 parts of water.An aliquot portion of this preparation was used in the following steps.I

A suspension, consistingrof 60parts distilled water l part of theabove-prepared cadmium phosphate, 0.008 part sodium oleate and 4.0.partsstyrene containing dissolvedin it 0.07part benzoyl peroxide (0.175%based on the styrene), was heated at 90 C. with stirring for 20 hours. 1The pH of the suspension medium was 5.6 at the time of completion of thepolymerization. Very fine beads 3 of an inch in diameter or less were'obtained. I

EXAMPLE 'XIV A su s'pensiongformed of 60 parts distilledwater, l 'part''hy'droxy "apatite (Figure 6) 0.003 part sodium dodecyl .ben'z'enersulfonate and. '40 parts of -mixeddichloro' styrenes containingdissolved therein: 0.02 'par't' benzoyl peroxide (0.05% based on thedichlorostyrenes) was heated at 80 C. for -20hours withstirring; Clearbeads having diameters of about: ,64; inch-were obtained;

The dispersingzagent usedin this example-and innExample 'XV' was shownby X-ray analysis to be'hydroxy apatite. Its particlezsizeis'illustrated in therelectronmicrograph ofv Figure 6- to be comparable tothat of Figure 1. EXAMPLE XV A'fsus'pension', formed"f1'om60' partsdistilled water;' 1 partihydroxy. apatite" (Figure 6), 0.008part'sodium'oleate and 40 'partsofmixe'd dichloro styrene's'containingdissolved t-herein 0.08 part b enzoyl peroxid'el (0.2% based on thedichlorostyren'esr, was heated at 801C.'f0r 20 hours with stirring;Clear beads about ,6 inch in diameter were obtained.

EXAMPLE XVI Asuspension, formed of 60 partsof distilled water, 1 "parthydroxy apatite (same particle size as in Example IV) ,0.008 part sodiumoleate and 40 parts of4'-vinyl pyridine containing dissolvedin it about0.08 part benzoyl peroxide (0.2 based on the vinylpyridine), wasagitated in a closedglass container at 90 C. for 16 hours. Fine beads 3inch in diameter or smaller were obtained.

EXAMPLEXVIL A: suspension, formed of 80 parts of distilled wateri l parthydroxy apatite (same particle size as in Example IV), 0.008 part sodiumoleate and 20 parts methylmethacrylate containing dissolved init'about0.035 part benzoyl peroxide (0.175% based on the methacrylate), washeated at 90C. with stirring for 20'hours. Very fine beads wereobtained.

EXAMPLE XVIII A-siispension, 'forme'd fro'm 75 parts of water, 1 part ofhydroxyapatite (same particle size as in Example IV) and 0.008 part ofsodium oleate, and 25 -parts of a'mix'ture of 16.6 parts styrene, 8.3parts 'vinyl'naphthalene and 0.044 part of benzoyl peroxide (0.175%based on the olefins), was'heated at 90C. with stirring for 20 hours.Very fine beads were obtained.

EXAMPLE XIX A suspension, formed of 70 parts of distilled water, 1-part-'hydroxy apatite (same particle size sisin Example IV), 0.008 partsodium oleate, and 30 parts of a mixture of 22.5 parts .styrene,7.5-parts ortho-monochlorostyrene and 0.06 part of-be'nzoyl' peroxide(0.2 based on the olefins) was agitated in a closed glass container for16 hours at 90 C. Fine beads were obtained.

EXAMPLE XX A suspension, formed from 60 parts water, 1 parthydroxyapatite" (same particle size as in Example 1V), 0.008 part sodiumoleate and 40 parts of a mixture of 36'par'ts of styrene, 4 parts of'acr'ylonitrile'and 0.07 part benzoyl' peroxide (0.175% based on' theolefins), was agitated'in a closed container at 90 C. for'16 hours. Finebeads were obtained.

EXAMPLEXXI A'rSllSPQI'lSIOIl, formed from 70 parts..water,'-.1 parthydroxy apatite (same particle size as in Example IV), 0.008 part sodiumoleate and. 30 parts of a mixture containing 28.5 parts styrene, 1.5parts lauryl methacrylate, and 0.06 part ben zoyl peroxide (0.2% basedon the olefins), was agitatedin a closed glass container at 90 C. for 16hours. Fine white beads'were obtained.

EXAMPLE XXII A suspension, formedof. parts of water, 1 part hydroxyapatite (same'particle size as in Example IV), 0.008 part sodium oleateand 20 partsof a mixture of 13 parts styrene, v7 parts dichloro styrene(mixed isomers) and 0.035 part benzoyl peroxide (0.175% based on theolefins), was stirred at C. for 20 hours. Fine beads were obtained.

EXAMPLE XXIII A suspension, formed of 80 parts'water', 1 part hydroxyapatite (same particle size as in- Example IV), 0.008 part sodium oleateand 20 parts of a mixture of 18 parts styrene, 2 parts acrylic acid, and0.035 part benzoyl peroxide (0.175% based on the olefins), was stirredat 90C. for 20 hours. Fine yellow beads were obtained.

EXAMPLE XXIV A suspension, formed of 50 parts water, 1 part hydroxyapatite (same particle size as in ExampleIV), 0.008 part sodiumoleateand 50 parts of a mixture of 25 parts of styrene, 25 parts'otvinylid'ene chloride and 0.087 part be'nzoylper oxide (0;175% based onthe-olefins), was stirred at 90" C. for 20 hours. Fine beads wereobtained.

EXAMPLE XXV A suspension, formed of 60 parts water, 'l'part hydroxyapatite (same particle size as in Example IV), 0.008 part sodium oleateand 40 parts of a mixture of 36 parts styrene, 4 parts butyl acrylateand'0.0'7 part benzoyl peroxide (0.175% based on the olefins), wasstirred at 90 C. for 20 hours. Fine beads were obtained.

EXAMPLE XXVI A suspension, formed of 88 parts wateryl part hydroxyapatite (same particle size as in Example IV), 0.008 part sodium oleateand 12 parts of a dehydrogenated diethylbenzene mixture'containing 3.6parts divinylbenzene, 8.4 parts other products of the dehydrogenation,and 0.21 part benzoyl peroxide (0.175% based on the hydrocarbons) wasstirred at 90 C. for 20 hours. Very fine beads were obtained.

Further, to modify, the properties-of the polymers and copolymersprepared in accordance with the practice of the invention, there may beincluded plasticisers such as dibutylphthalate and butyl Cellosolvestearate,.aswell as dyes, opacifiers, mold lubricants and the like.

In place of benzoyl peroxide therev may be substituted otherpolymerization catalysts. Preferably, the catalysts should be soluble.in styrene or in whatever. pol-ymerizableethylenic monomer is used.Thus,..in-p1ace of benzoyl. peroxide there maybe used acetylperoxidetertiary-butyl hydrop'eroxide, ditertiarybutyl peroxide,- laurylperoxide, phthalyl peroxide, tetrahydrophthalyl peroxide, succinylperoxide, etc., and combinations of these.

The amountof catalyst may be varied according to the nature and activityof the particular catalyst, according to the nature of the particularpolymerizable material, and according to the product desired. Anespecial advantage is ob tained in polymerizations according to thepresent invention in that the amount of catalyst may be varied over awide range or even omitted. It is advantageous, particularly where beadpolymers suitable for injection molding are desired, to keep thecatalyst activation below that equivalent at about 90 C. to about 0.3%benzoyl peroxide based upon the polymerizable ethylenio monomer. Byusing this low catalytic activation coupled with a phosphate dispersingagent extended by an anionic surface-active agent in accordance with theinvention it is possible to obtain high molecular weight polymers.Moreover, by means of the present invention, it is possible to maintainan extraordinarily high ratio of olefin to water, e. g., 1-3 parts ofpolymerizablc ethylenic monomer for each part of water, and at the sametime produce tough, high molecular weight polymers suitable forinjection molding.

The temperature may be varied according to the nature of thepolymerizable material used and the type of polymer desired. Ordinarily,however, for styrene a temperature somewhat be low the boiling point ofwater, say about 90 or 95 C. will be advantageous unless thepolymerization is carried out in a pressure vessel. The use of pressureand the higher temperatures obtainable thereby may be usedadvantageously to speed up the polymerization. Pressure vessels may alsobe used advantageously for the more volatile polymerizable materials.

The pH of the dispersion medium may be varied over a wide range withoutapparent efiect on the stability of the suspension or thepolymerization. It should be borne in mind, however, that if the pH istoo high, peroxide catalysts, such as benzoyl peroxide, will beinactivated and if it is too low the acid soluble phosphate will besolubilized or chemically changed. It is desirable, therefore, tooperate with a pl-I ranging between about 3 and 8, until the finalwashing operation when the pH may be reduced to about 2 in order tosolubilize the phosphate dispersing agent.

While the invention has been described with reference to particularembodiments thereof, it will be understood that in its broader aspectsthe invention is not limited thereto, but the invention may be variouslyembodied within the scope of the invention as set forth herein and inthe appended claims.

The use of an anionic surface-active agent as an extender for aphosphate dispersing agent disclosed herein is claimed in my presentlycopending application Serial No. 255,590, filed November 9, 1951.

What is claimed is:

1. In a process for preparing polymer beads, the steps of forming anaqueous suspension by adding to water in one portion a polymerizable.said ethylenic monomer to water is no less than 1:1.

2. The process'oi claim 1, in which the polymerizable compositioncomprises a vinyl aromatic compound.

3. The process of claim 1, in which the polymerizable compositioncomprises styrene.

4. The process of claim 1, in which the phosphate is hydroxy apatite.

5. The process of claim 1, in which the polymerizable compositioncomprises a vinyl aromatic compound and the phosphate is hydroxyapatite.

6. The process of claim 1, in which the polymerizable compositioncomprises styrene and the phosphate is hydroxy apatite.

7. The process of claim 1, in which the phosphate is tricalciumphosphate.

8. The process of claim 1, in which the phosphate is trimagnesiumphosphate.

9. The process of claim 1, in which the polymerizable compositioncomprises a vinyl aromatic compound and the phosphate is trimagnesiumphosphate.

10. The process of claim 1, in which the polymerizable compositioncomprises styrene and the phosphate is trimagnesium phosphate.

11. The process of claim 1, in which the phosphate is tribariumphosphate.

12. The process of claim 1, in which the phosphate is a syntheticcalcium phosphate having a ratio by weight of CaO/PzOs at least equal to1.3, said phosphate being prepared by the reaction of orthophosphoricacid and calcium oxide.

13. The process of claim 12, in which the polymerizable compositioncomprises styrene. I

JOHN MARSHALL GRIM.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,171,765 Rohm Sept. 5, 1939'2,279,436 Berg Apr. 14, 1942 2,440,808 Neher May 4, 1948 2,524,627Hohenstein Oct. 3, 1950 OTHER REFERENCES Hohenstein et al., J. PolymerScience, 1, 127-145, especially page 139 (March 1946).

1. IN A PROCESS FOR PREPARING POLYMER BEADS, THE STEPS OF FORMING ANAQUEOUS SUSPENSION BY ADDING TO WATER IN ONE PORTION A POLYMERIZABLECOMPOSITION COMPRISING A POLYMERIZABLE ETHYLENIC MONOMER, STABILIZINGSAID SUSPENSION BY MEANS OF FROM ABOUT 0.1% TO ABOUT 5% BY WEIGHT BASEDON THE SYSTEM OF A PHOSPHATE, DIFFICULTLY SOLUBLE IN WATER ANDCONTAINING FOR EACH PHOSPHATE GROUP AT LEAST THREE EQUIVALENTS OF AMETAL, THE CARBONATE OF WHICH IS AT MOST BY SLIGHTLY SOLUBLE IN WATER,SAID PHOSPHATE BEING COMPRISED OF PARTICLES PREDOMINANTLY OF A SIZE INTHE RANGE 0.2-0.005 MICRON, AND EFFECTING POLYMERIZATION OF SAIDETHYLENIC MONOMER WHILE THUS DISPERSED, IN WHICH PROCESS THE RATIO INPARTS BY WEIGHT OF SAID ETHYLENIC MONOMER TO WATER IS NO LESS THAN 1:1.